1. Field of the Invention
The present invention relates generally to implantable medical devices, and more particularly, to a complementary drug delivery sheath for an implantable medical device.
2. Related Art
Implantable medical devices are capable of providing a wide range of benefits to a patient. For example, implantable prosthetic hearing devices process ambient sound to supplement or provide hearing ability to hearing impaired patients (sometimes referred to herein as “recipients”).
Implantable prosthetic hearing devices include a category of implantable devices known as Cochlear™ implants (also referred to as Cochlear™ devices, Cochlear™ implant devices, and the like; “cochlear implants” herein). (COCHLEAR is a trademark of Cochlear Limited, Lane Cove, NSW, Australia.) In cochlear implants, an array of stimulation electrodes is implanted in a recipient's cochlea. This array is controlled by an electronic system encased in a hermetically sealed, biocompatible housing typically implanted in the mastoid. The electronic system essentially contains decoder and driver circuits for the stimulation electrodes. Acoustic sound reception and conversion of acoustic signals into electrical signals typically occurs externally in a sound processor worn by the recipient. The sound processor superimposes the preprocessed signals, properly coded, on a high frequency carrier signal which is transmitted transcutaneously to the implanted components through the closed skin. A microphone is located outside of the recipient's body, typically in a behind-the-ear housing worn on the auricle.
Traditionally, there has been interest in delivering bioactive substances or chemicals (generally and collectively referred to herein as “drugs”) in conjunction with a cochlear implant and other implantable medical devices for a variety of purposes. For example, in one conventional approach the implantable medical device is coated with a bioactive substance. In another conventional approach a bioactive substance is integrated into the polymeric coating of the implantable medical device. In other conventional approaches various techniques for delivering drugs in liquid form to a target location in a patient from an external or implanted reservoir.
These and other conventional approaches typically require the incorporation of the drug into the implantable medical device during the manufacturing process of the device. This introduces a number of difficult problems and challenges for the manufacturing and sterilization processes, particularly for complex implantable medical devices. On the other hand, the use of reservoirs provides significant limitations to many aspects of the administration of the drug therapy.